Abstract

Ag nanostructures with surface-enhanced Raman scattering (SERS) activities have been fabricated by applying laser-direct writing (LDW) technique on silver oxide (AgOx) thin films. By controlling the laser powers, multi-level Raman imaging of organic molecules adsorbed on the nanostructures has been observed. This phenomenon is further investigated by atomic-force microscopy and electromagnetic calculation. The SERS-active nanostructure is also fabricated on transparent and flexible substrate to demonstrate our promising strategy for the development of novel and low-cost sensing chip.

Figures (4)

(a) Optical reflection image of laser-generated Ag nanostructures made with laser powers 21 mW, 11 mW, 7 mW, respectively and (b) the corresponding Raman intensity map of R6G on the Ag nanostructures. The Raman intensity map is obtained from integrating spectral intensity of the R6G Raman peak ranging from 598 to 623 cm−1. The two images are shown on the same scale. (c) Raman spectra of R6G adsorbed on various zones of laser-processed AgOx thin film. The up insert shows the molecular structure of R6G molecule, and the button insert is the magnified Raman spectrum of R6G molecules obtained from the region of unprocessed AgOx thin film.

(a)-(c) 2D AFM images of laser-generated Ag nanostructures with processing laser powers 21 mW, 11 mW, and 7 mW, respectively. The three images are shown on the same scale. (d)-(f) are the corresponding 3D AFM images, and (g)-(i) are the corresponding histograms of Ag NP diameters generated with various laser powers. The height scales in the 2D- and 3D- AFM images are properly adjusted for clearly demonstrating the differences of the surface morphologies between the three Ag nanostructures.

Raman spectra of R6G molecules obtained from the laser-generated Ag nanostructure and as-deposited AgOx thin film on optical transparent and flexible substrate. The Raman image of intensity map shows the spatial distribution of Raman intensity integrated over the peak in the regime of 598-623 cm−1